The Coanda effect dictates that liquid tends to adhere to the inner surface of a curve when flowing through a pipe. Fluid flow generally follows the Navier-Stokes equations, which govern its movement.
Laminar flow, which occurs in a perfectly temperature-controlled, frictionless pipe, represents a smooth movement. Contact with the pipe walls reduces the fluid speed at the edges, establishing what is known as the boundary layer.
Consequently, any bend within the pipe generates a spiral pattern due to this boundary layer effect. Furthermore, any curve, valve, or pump possesses the capacity to induce spiralling within the fluid.
Deflecting the liquid, even through microscopic defects or slight temperature changes, can create a small eddy or swirl. The boundary layer dampens swirls if the liquid moves at a sufficiently slow pace.
However, when the liquid surpasses a critical speed, swirls begin to develop because of non-linear factors. Turbulent flow is characterised by unpredictable surging and thrashing motions.
Slowing the liquid's movement proves helpful in stopping the onset of turbulence. A long, straight pipe can settle the flow if its speed remains below the critical turbulence speed.
Researchers estimate that after passing through a single curve, the required length for settling the flow is approximately 15 times the pipe's diameter. Flow conditioners can restore laminar flow by either dividing the pipe into smaller sections or by incorporating flat plates fitted with holes.
